the procedure described here ZCS 6.0:Zimbra REST API Reference:Import Contactsworks - Zimbra :: Wiki works fine for uploading .csv files.

2 questions:

#1 Is there a way to avoid duplicate message upload (if I do the same command twice, I have all entries twice)

#2 Does anybody know how to modify the curl command in order not to upload a file, but to import data from another server (that provides a csv file from)?

Here is the link that provides the csv file: